I have the same issue on my iPhone 4S in the UK and previously on my iPhone 4 too. The only solution seems to be a reboot of the phone, and it will work for a day or two, but then i have to reboot the phone again to get push working.
It is a total pita, as you dont realise that push isnt working initially, until you manually check for mail.
It is a total pita, as you dont realise that push isnt working initially, until you manually check for mail.